python - Django 表单错误 : Select a valid choice. That choice is not one of the available choices

Question

我正在尝试创建一个带有两个下拉菜单的网站:部门和类(class)编号。下拉菜单的数据来 self 的 SQL 数据库的“类(class)”表。现在我的网站正确初始化并在下拉菜单中显示正确的选项。然而，当用户在下拉菜单中选择一个选项并提交他们的选择时，Django 抛出一个“选择一个有效的选择。该选择不是可用的选择之一。”错误。我怀疑我的表单输出格式不正确，因此无法在我的数据库中找到选择，但我已经阅读了许多其他具有相同问题的 SO 问题，但仍然一无所获。感谢您的帮助。

模型.py

from django.db import models

class Dept(models.Model):
    dept = models.CharField(max_length=255, db_column = 'dept')
    class Meta:
        managed = False
        db_table = 'courses'
    def __str__(self):
        return self.dept

class Course_num(models.Model):
    course_num = models.CharField(max_length=255, db_column = 'course_number')
    class Meta:
        managed = False
        db_table = 'courses'
    def __str__(self):
        return self.course_num

表单.py

from django import forms
from .models import *

class CourseForm(forms.Form):
    dept = forms.ModelChoiceField(
        queryset=Dept.objects.values_list('dept', flat = True).distinct().\
            order_by('dept').exclude(dept__isnull=True),
        required=False,
        empty_label="No preference",
        label=u"Department")

    course_num = forms.ModelChoiceField(
        queryset=Course_num.objects.all().\
            order_by('course_num').values_list('course_num', flat = True).\
            distinct().exclude(course_num__isnull=True),
        required=False,
        empty_label="No preference",
        label=u"Course Number")

views.py

def home(request):
    context = {}
    res = None
    form_CourseForm = CourseForm()
    if request.method == 'GET':
        form_CourseForm = CourseForm(request.GET)
        args = {}
            if form_CourseForm.is_valid():
            dept = form_CourseForm.cleaned_data['dept']
            if dept:
                args['dept'] = dept
            course_num = form_CourseForm.cleaned_data['course_num']
            if course_num:
                args['course_num'] = course_num
    ...

Answer 1

改变你的查询集并尝试

class CourseForm(forms.Form):
    dept = forms.ModelChoiceField(
        queryset=Dept.objects.distinct().
        order_by('dept').exclude(dept__isnull=True),
        required=False,
        empty_label="No preference",
        label=u"Department")

    course_num = forms.ModelChoiceField(
        queryset=Course_num.objects.distinct().
        order_by('course_num').exclude(course_num__isnull=True),
        required=False,
        empty_label="No preference",
        label=u"Course Number")